The present invention relates to a process for the preparation of diacetone-ketogulonic acid, a valuable intermediate in the preparation of vitamin C.
In the preparation of diacetone-ketogulonic acid, the starting material generally is diacetonesorbose. This can be oxidized to diacetone-ketogulonic acid, for example with inorganic oxidizing agents, such as HNO.sub.3, H.sub.2 O.sub.2 or hypochlorite. Catalyzed oxidation with air or oxygen-containing gases, and also electrochemical oxidation, have recently aroused particular interest. In these processes, very good conversions are achieved at the start of the reaction, but the reaction becomes progressively slower as the content of the oxidation product increases. To achieve complete conversion of the diacetonesorbose, it is necessary to employ relatively long reaction times and more rigorous conditions. Concomitantly, there is the danger of further oxidation of the already formed diacetone-ketogulonic acid, which leads to a reduction in yield and to undesired by-products.